Brian Beesley (Mersenne Digest 715, 7. April) wrote:
>There are also factoring programs available in portable
>high-level-language source format, in particular look
>for Mfactor.c If it wasn't for the fact that factoring
>is so far ahead of LL testing, I'd probably switch my
>Alpha system to factoring - with its 64 bit integer
>registers and quad-issue pipeline, the architecture is
>much better suited to factoring than LL testing, and
>the performance is somewhat startling for factoring
>(up to 63 bits) even though the program is neither
>tuned to the hardware nor hand optimized.
True, the generic-C component of Mfactor is not tuned to
any particular hardware. But Peter Montgomery (author of
Mfactor) has written assembly code supplements for two
architectures (Alpha and MIPS) which support
64 x 64 ==> 128-bit integer multiply, and thus on those
platforms the program is very speedy. On the MIPS and
pre-21264 Alphas (which don't fully pipeline integer
multiply) the single functional unit that does integer
multiply is saturated and thus Mfactor may not perform
as well on a cycle-by-cycle basis as one would hope for,
but the performance should still be quite good. On the
Alpha 21264 (which fully pipelines IMUL) Mfactor should
really scream, but of course the 21264 is extremely good
at the floating-point ops that dominate an Mlucas run,
too. The Sparc, alas, has a very poor integer multiply
capability and should be used for floating-point work
(i.e. LL testing) only.
I think the suggestion to have one machine (whether that
be a PC running Prime95 or a MIPS or Alpha running
Mfactor) do all the factoring needed to keep multiple
non-PC machines well-fed with exponents is a good one,
since otherwise, juggling factoring and LL work becomes
a pain. Note that Mfactor (as currently configured)
doesn't support putting multiple exponents into a to-do
file, so the best way to trial factor lots of exponents
is probably just to paste the one-line inputs needed for
the exponents, one after another, into the same window -
when the program finishes the current exponent, it'll
read the next input line from the buffer. Of course,
this doesn't permit one to log out, so is best done on
a machine which one owns (then one can at least lock the
display when one needs to leave.)
Mfactor (source and precompiled binaries for MIPS/Irix
and Alpha/Unix) is available at my ftp site:
ftp://209.133.33.182/pub/mayer/README.html
Happy hunting,
-Ernst
_________________________________________________________________
Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm
Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
